Thermography

Thermography images the infrared radiation emitted from a surface and evaluates anomalies in the temperature distribution. Passive thermography observes existing temperature differences; active thermography applies controlled heat to the structure to reveal sub-surface flaws.

The aim is to detect, without contact, pre-failure heating in electrical and mechanical equipment, heat loss in buildings and delamination in composite structures.

• Electrical panels and switchgear
• Mechanical equipment: bearings, couplings, motors
• Building envelope and insulation assessment
• Delamination in composite structures
• Refractory and furnace linings
• Steam traps and process lines

NDT has no interval of its own; how often it is applied follows the inspection programme it serves. In manufacturing the governing factor is the coverage required by the product standard and the specification (e.g. a given percentage of welds); in operation it is the asset integrity or risk-based inspection programme.

• Abnormal hot or cold spots
• Temperature difference from reference points (ΔT)
• Insulation losses and thermal bridges
• Moisture-related temperature anomalies
• Subsurface delamination and voids (in active thermography)
• Accounting for emissivity and reflection effects

• ISO/IEC 17020
• ISO 18434-1
• ISO 10878
• ISO 6781
• ASTM E1934
• ISO 9712

• Calibrated infrared thermal camera
• Ambient temperature, humidity and wind meter
• Emissivity reference tapes and contact thermometer
• Heat source (for active thermography: flash, lamp, induction)
• Analysis and reporting software

1. 1Selection of Method and TechniqueThe type and location of the discontinuity sought and the material properties are assessed to select a suitable method and technique; a written procedure is prepared.
2. 2Verification of Personnel and EquipmentThe level and industrial-sector qualification of the operator under EN ISO 9712 and the calibration records of the equipment are checked.
3. 3Surface PreparationThe inspection surface is prepared as the method requires; coating, rust and contamination directly affect the sensitivity of the method.
4. 4Calibration and Sensitivity VerificationA reference block or control specimen is used to demonstrate that the system can detect the discontinuity sought.
5. 5Performing the InspectionScanning is carried out according to the procedure; indications are recorded and located.
6. 6AssessmentIndications are evaluated against the applicable acceptance standard to determine whether they are defects; they are sized.
7. 7ReportingMethod, technique, equipment, calibration, findings and acceptance criteria are reported together.

Findings are graded by temperature difference and the criticality of the affected component. The most common error in thermography is an incorrect temperature reading due to emissivity and reflection not being accounted for; for this reason, surface conditions are stated in the report.

• The inspection body and the personnel's EN ISO 9712 level and sector
• Method and technique applied and the written procedure number
• Part and weld examined, with a location sketch
• Equipment, consumables and calibration records
• Surface condition and inspection conditions
• Indications recorded, with their location and size
• Acceptance standard applied and the result of the evaluation
• Accept / reject decision

Non-destructive testing is carried out as an accredited inspection activity under ISO/IEC 17020. The second decisive factor in NDT is personnel qualification: the operator must be certified under EN ISO 9712 for the method, level and industrial sector concerned. An examination performed with a method outside the scope of that certificate is not valid. EUROLAB holds internationally recognised accreditation under ISO/IEC 17020, granted by accreditation bodies that are signatories to the ILAC mutual recognition arrangement.

• VT Visual
• PT Penetrant
• MT Magnetic Particle
• UT Ultrasonic
• RT Radiographic
• ET Eddy Current
• PAUT
• TOFD